Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Self organization in 3GPP long term evolution networks

Mobiele en breedbandige internettoegang is realiteit. De internetgeneratie vindt het immers normaal om overal breedbandige internettoegang te hebben. Vandaag zijn er al 5,9 miljard mobiele abonnees ( 87% van de wereldbevolking) en 20% daarvan hebben toegang tot een mobiele breedbandige internetverbinding. Dit wordt aangeboden door 3G (derde generatie) technologieën zoals HSPA (High Speed Packet Access) en 4G (vierde generatie) technologieën zoals LTE (Long Term Evolution). De vraag naar hoogkwalitatieve diensten stelt de mobiele netwerkoperatoren en de verkopers van telecommunicatieapparatuur voor nieuwe uitdagingen: zij moeten nieuwe oplossingen vinden om hun diensten steeds sneller en met een hogere kwaliteit aan te bieden. De nieuwe LTE-standaard brengt niet alleen hogere pieksnelheden en kleinere vertragingen. Het heeft daarnaast ook nieuwe functionaliteiten in petto die zeer aantrekkelijk zijn voor de mobiele netwerkoperator: de integratie van zelfregelende functies die kunnen ingezet worden bij de planning van het netwerk, het uitrollen van een netwerk en het controleren van allerhande netwerkmechanismen (o.a. handover, spreiding van de belasting over de cellen). Dit proefschrift optimaliseert enkele van deze zelfregelende functies waardoor de optimalisatie van een mobiel netwerk snel en automatisch kan gebeuren. Hierdoor verwacht men lagere kosten voor de mobiele operator en een hogere kwaliteit van de aangeboden diensten

Stochastic transport in complex environments : applications in cell biology

Living organisms would not be functional without active processes. This general statement is valid down to the cellular level. Transport processes are necessary to create, maintain and support cellular structures. In this thesis, intracellular transport processes, driven by concentration gradients and active matter, as well as the dynamics of migrating cells are studied. Many studies deal with diffusive intracellular transport in the complex environment of neuronal dendrites, however, focusing on a few spines. In this thesis, a model was developed for diffusive transport in a full dendritic tree. A link was established between complex structural changes by diseases and transport characteristics. Furthermore, recent experimental studies of search processes in migration of dendritic cells show a link between speed and persistence. In this thesis, a correlation between them was included in a stochastic model, which lead to increased search efficiency. Finally, this thesis deals with the question of how active, bidirectional transport by molecular motors in axons can be efficient. Generically, traffic jams are expected in confined environments. Limitations of bypassing mechanisms are discussed with a bidirectional non-Markovian exclusion process, developed in this thesis. Experimental findings of cooperative effects and microtubule modifications have been incorporated in a stochastic model, leading to self-organized lane-formation and thus, efficient bidirectional transport.Ohne aktive Prozesse wären lebendige Organismen nicht funktionsfähig. Dies gilt bis herab zur Zellebene. Transportprozesse sind notwendig um zelluläre Strukturen aufzubauen und zu erhalten. In dieser Arbeit werden intrazelluläre Transportprozesse, getrieben von Konzentrationsgradienten und aktiver Materie, sowie die Dynamik in Zellmigration untersucht. Viele Studien beschäftigen sich mit passivem Transport in der komplexen Umgebung von neuronalen Dendriten, vorwiegend jedoch mit einzelnen Dornvortsätzen (spines). In dieser Arbeit wurde ein Modell zu Diffusion in einer vollständigen Dendritenstruktur entwickelt und eine Relation zwischen Krankheitsverläufen und neuronalen Funktionen gefunden. Die Migration von dendritischen Zellen zeigen einen Zusammenhang zwischen ihrer Geschwindigkeit und Persistenz. Dieser wurde in ein stochastisches Modell übernommen welches zeigte, dass die Sucheffizienz der Zellen damit gesteigert werden kann. Außerdem geht es um die Frage wie aktiver, bidirektionaler Transport durch molekulare Motoren in Axonen effizient sein kann. In einem so begrenzten Raum sind Verkehrsstaus zu erwarten. In dieser Arbeit wurden lokale Austauschmechanismen anhand des entwickelten Nicht-Markovschen, bidirektionalen Exklusionsprozess diskutiert. Experimentell entdeckte kooperative Effekte und Mikrotubulimodifikationen wurde in ein stochastisches Modell übernommen, was zu selbstorganisierter Spurbildung und damit zu effizientem bidirektionalem Transport führte

An optimal nephelometric model design method for particle characterisation

Scattering nephelometry is a particle characterisation method applicable to fluid suspensions containing impurities. Solutions derived by the method feature particle classification by size (diameter), volume or texture as well as continuous on-line and in-situ monitoring, The replacement of turbidimeters with nephelometers in many existing turbidity applications could result in suppression of side effects caused by limitations and uncontrolled parameter drifts and satisfaction of problem-defined constraints at virtually no change in implementation cost. A major issue of nephelometric model design is the selection of a mathematical tool suitable for the modelling of the data analysis system. [Continues.

Underwater simulation and mapping using imaging sonar through ray theory and Hilbert maps

Mapping, sometimes as part of a SLAM system, is an active topic of research and has remarkable solutions using laser scanners, but most of the underwater mapping is focused on 2D maps, treating the environment as a floor plant, or on 2.5D maps of the seafloor. The reason for the problematic of underwater mapping originates in its sensor, i.e. sonars. In contrast to lasers (LIDARs), sonars are unprecise high-noise sensors. Besides its noise, imaging sonars have a wide sound beam effectuating a volumetric measurement. The first part of this dissertation develops an underwater simulator for highfrequency single-beam imaging sonars capable of replicating multipath, directional gain and typical noise effects on arbitrary environments. The simulation relies on a ray theory based method and explanations of how this theory follows from first principles under short-wavelegnth assumption are provided. In the second part of this dissertation, the simulator is combined to a continous map algorithm based on Hilbert Maps. Hilbert maps arise as a machine learning technique over Hilbert spaces, using features maps, applied to the mapping context. The embedding of a sonar response in such a map is a contribution. A qualitative comparison between the simulator ground truth and the reconstucted map reveal Hilbert maps as a promising technique to noisy sensor mapping and, also, indicates some hard to distinguish characteristics of the surroundings, e.g. corners and non smooth features.O mapeamento, às vezes como parte de um sistema SLAM, é um tema de pesquisa ativo e tem soluções notáveis usando scanners a laser, mas a maioria do mapeamento subaquático é focada em mapas 2D, que tratam o ambiente como uma planta, ou mapas 2.5D do fundo do mar. A razão para a dificuldade do mapeamento subaquático origina-se no seu sensor, i.e. sonares. Em contraste com lasers (LIDARs), os sonares são sensores imprecisos e com alto nível de ruído. Além do seu ruído, os sonares do tipo imaging têm um feixe sonoro muito amplo e, com isso, efetuam uma medição volumétrica, ou seja, sobre todo um volume. Na primeira parte dessa dissertação se desenvolve um simulador para sonares do tipo imaging de feixo único de alta frequência capaz de replicar os efeitos típicos de multicaminho, ganho direcional e ruído de fundo em ambientes arbitrários. O simulador implementa um método baseado na teoria geométrica de raios, com todo seu desenvolvimento partindo da acústica subaquática. Na segunda parte dessa dissertação, o simulador é incorporado em um algoritmo de reconstrução de mapas contínuos baseado em Hilbert Maps. Hilbert Maps surge como uma técnica de aprendizado de máquina sobre espaços de Hilbert, usando mapas de características, aplicadas ao contexto de mapeamento. A incorporação de uma resposta de sonar em um tal mapa é uma contribuição desse trabalho. Uma comparação qualitativa entre o ambiente de referência fornecido ao simulador e o mapa reconstruído pela técnica proposta, revela Hilbert Maps como uma técnica promissora para mapeamento atráves de sensores ruidosos e, também, aponta para algumas características do ambiente difíceis de se distinguir, e.g. cantos e regiões não suaves

Solar Seismology from Space. a Conference at Snowmass, Colorado

The quality of the ground based observing environment suffers from several degrading factors: diurnal interruptions and thermal variations, atmospheric seeing and transparency fluctuations and adverse weather interruptions are among the chief difficulties. The limited fraction of the solar surface observable from only one vantage point is also a potential limitation to the quality of the data available without going to space. Primary conference goals were to discuss in depth the scientific return from current observations and analyses of solar oscillations, to discuss the instrumental and site requirements for realizing the full potential of the seismic analysis method, and to help bring new workers into the field by collecting and summarizing the key background theory. At the conclusion of the conference there was a clear consensus that ground based observation would not be able to provide data of the quality required to permit a substantial analysis of the solar convection zone dynamics or to permit a full deduction of the solar interior structure